GB2027535A

GB2027535A - Cooling device for hot gases in pipes

Info

Publication number: GB2027535A
Application number: GB7925807A
Authority: GB
Original assignee: Sidepal SA
Current assignee: Sidepal SA
Priority date: 1978-07-24
Filing date: 1979-07-24
Publication date: 1980-02-20
Also published as: NO792425L; JPS5549694A; DE2927434C2; PL217221A2; SE7906219L; SE438202B; RO78689A; CH641552A5; NO146151B; DK308979A; ZA793326B; DD144953A5; LU80033A1; NO146151C; ATA506679A; SU876072A3; BE877853A; BR7904747A; ES482678A1; IT1122279B

Description

1 GB 2 027 535 A 1

SPECIFICATION

Cooling device for hot gases in pipes The invention relates in general to heat exchangers and in particular to a new and useful cooling device for hot gases in pipes, particularly for hot waste gases from industrial furnaces.

Although the cooling device to which the inven- 0 tion relates can in principle be used in any gas pipe in which hot gases are to be cooled, it will be described hereinafter by reference to the concrete example of its use in industrial furnace waste pipes fitted with a fresh-air intake. Waste gas or gas suction removal pipes of this kind, with a fresh-air intake, whether or not the latter can be regulated, are already known, for example, from electric arc furnaces for the electrical production of steel.

With these furnaces, for reasons explained in detail, for example, in Luxembourg patent No. 80,034 of July 24,1978, an adjustable intake for additional air or fresh air is preferably provided, downstream of a throttle device, in the gas suction pipe. One purpose of this air intake is to ensure afterburning of the hot waste gases from the furnaces and also to cool the gases.

The cooling of the gases is assisted by a usually water cooled piece of piping for waste gas, preferably designed on the "pipe-to-pipe" principle, con- nected up at the point where the intake for additional air is provided in the piping system and hereinafter briefly termed "connection pipe" or "connection piece".

This water-cooled connection pipe, in order to keep the cost moderate and ensure that it does not occupy excessive space, should not be allowed to exceed a certain length, approximately 15 m, but over this length of the connecting pipe, it is desired to cool the gases down by at least 400 'c.

For reasons of energy economy, the proportion of the cooling effect provided by the water-cooled connection pipe by comparison with the part of the cooling action exerted by the additional air should be as great as possible since not only does the heating undergone by the cooling water represent recoverable energy but a high proportion of fresh air would entail the direct loss of this otherwise recoverable energy, besides which, still more efficient exhauster fans would be required. The practical conclusion to be drawn from these circumstances is that the supply of fresh air should be kept to the indispensable minimum and the hot waste gases brought into as intimate contact as possible with cooling elements which, if necessary, enable energy to be recovered in a usable form. It will be evident from the foregoing that the cooling pipes of the connection pipe constitute cooling elements of this kind.

The fresh air, at a relatively low temperature,is nevertheless fed in at that point on the periphery of the waste gas pipe at which the gases enter the connection pipe. In the latter, therefore, a kind of "funnel" occurs, i.e. a peripheral layer of low temperature fresh air containing a hot "core" of gas.

This flow configuration suffers from the dual draw- back that the air and gas are only incompletely mixed together, disproportionately large quantities of air therefore being required for the after -burning of the gas, and that the hot gases, contrary to the purpose in view are kept away by the tubular ---funneV' of air from the pipe walls to be cooled.

Even if no hose-shaped funnel formed, however, perhaps because suitable measures had been taken to effect the intensive mixing of incoming fresh and of hot gases, it would still not be possible to ensure optimum contact between the entire volume of the mixture on its comparatively short passage through the connection pipe.

The purpose of the invention is to provide a cooling device which will largely eliminate the drawbacks and inadequacies of existing systems, by considerably intensifying, with simple means,the cooling effect exerted on the waste gases passing through a certain section of the waste gas piping and by rendering recoverable the energy dissipated in this process.

This purpose is achieved by means of a cooling device characterized by cooling registers forming part of a vapour or liquid cooled "pipe-to-pipe" construction and installed so that they extend into the waste-pipe transversally to the direction of flow of the waste gases.

The invention provides a cooling device for use in a tubular hot gas conduit which is made up of longitudinally arranged pipes disposed in side by side abutting relationship around the conduit circumference, a plurality of registers connected into one of the pipes and disposed in space relationship along the length of the conduit. Each register extends transverse to the flow direction through the conduit and they include one or more substantially U-shaped pipes which are connected externally of the conduit to an inlet for the flow of cooling fluid from one side of the conduit to the other and then backwardly to an outlet.

The various features which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

In the drawings Figure 1 is a front elevational view of a partly broken away section of waste-gas piping, with cooling registers extending into it constructed in accordance with the invention, and Figure 2 is a section taken along the line A-B of Figure 1.

Referring to the drawings in particular, the invention embodied therein, comprises, a cooling device for use in a tubular hot gas conduit, generally designated 8. The tubular hot gas conduit 8 includes a damper portion 6 which is adjustable in respect to the pipe end or connection piece 4. The hot gas conduit 8 is of a type in which an end thereof may be adjusted relative to the pipe end 4 so as to form a gap 18 of varying size for the inflow of a cooling air into the hot gas line which may also supply air for 2 GB 2 027 535 A 2 additional combustion of the hot gases as they flow through the hot gas pipe 8. The cooling device in accordance with the invention comprises a plurality of registers 10, 12, 14 and 16 which are arranged in spaced relationship in respect to the direction of flow indicated by the arrow 18'and they extend from one side of the hot gas conduit 8 into closely spaced relationship with the opposite side.

Figure 1 shows a section of waste-gas piping belonging, for instance, to an electric arc furnace and consisting of a pipe end 4, which may, for example, be the downstream end of the elbow of the furnace, and of a regulator 6 for additional air, in accordance with Luxembourg patent No. 80.034, and also a vapour-or-water-cooled gas conduit 8, constructed on the "pipe-to-pipe" principle, into which cooling registers 10, 12,14 and 16 are built, these latter taking the form of a likewise vapour-or-liquid-cooled pipe-to-pipe construction and being built into the connection pipe in succession to one another as viewed in the direction of flow 18' of the gases and positioned perpendicularly to the flow direction. An air gap 18 ensures the constant supply of a certain minimum quantity of additional air from the sur- rounding areas.

The additional air can be advantageously controlled by the regulating device 6 in accordance with the aforementioned Luxembourg patent. In this process, the tube part includes segmental dampers 20, 22, 20', 22'which are actuated by hydraulic jackets, of which, for the sake of simplicity only two are shown, i.e. 24 and 24'. Dampers 20. 22, 20', 22'are either opened or closed with a "tulip-type" movement.

As may be easily seen from Figure 1, the cold air flowing in at 18 will inevitably cause a colder marginal layer to form along the inner wall of the pipe 8, as a result of which the desired cooling of the hot waste gases will be at all events seriously impeded if special counter-measures are not adopted.

According to the invention, cooling registers generally designated 10, 12, 14 and 16, are disposed across hot gas conduit 8 and are located at spaced locations along the length of the connection pipe.

Each register is in the form of a vapour-cooled, or preferably watercooled "pipe-to-pipe" construction. Each of these cooling registers possesses an inlet 26 and an outlet 28, between which the cooling water circulates between connected U-shaped tubes up and down a number of times on the serpentine principle (Figure 1). In the case of each register, e.g. the register 10, certain numbers of these serpentines are connected in parallel to one common inlet water tank portion or header 1 W'. This parallel arrange- ment of individual serpentines may also be seen in Figure 2. The serpentines of two registers succeeding each other as viewed in the direction of flow of the gases, as shown by arrow 18'are preferably offset in respect to each other, as may be seen from the references 14k, 16k, 14k+1 and 16k+1 of individual serpentines selected from the registers 14 and 16. This staggered arrangement ensures the best possible contact between the hot waste gases and the cooling pipes of the registers.

-65 In addition to a direct cooling action on the gases flowing through the system the invention also ensures a certain turbulent motion in the said gases, thus improving not only the contact with the cooling pipes of the cooling registered themselves but also the contact with the wall of the cooled gas conduit 8, as the hose-shaped "funnel" of cold air coming in from gap 18 as mentioned previously is destroyed byturbulence.

As maybe seen from the drawings, the registers are inserted into the gas conduit 8 individually, preferably from the top, and are affixed to one common baseplate 30. The operation of dismantling the registers for maintenance or repair, or in order to remove deposits of dust from the gas conduit 8, thus presents no difficulty. The registers are preferably constructed as modules, and the number of these installed can vary according to the cooling requirements. Upon the removal of a register, the opening can be closed with a blind cover of the size of the baseplate 30.

Claims

CLAIMS:

1. A cooling device for use in a tubular hot gas conduit which is made up of longitudinal pipes arranged in side by side abutting relationship around the conduit circumference, said conduit having a gas flowtherethrough in a longitudinal direction, comprising a plurality of registers arranged in spaced relationship along the length of said conduit and extending across said conduit transverse to the flow direction, each of said registers including a plurality of tubes connected into one side of said hot gas conduit and extending through said hot gas conduit substantially to the other side thereof, each of said tubes having an inflow portion extending into said hot gas conduit from one side, flow to the opposite side and an outlet portion with a flow from said opposite side to the one side and for the outflow of a cooling medium.

2. A cooling device according to claim 1 wherein said tubes comprise a plurality of substantially U-shaped tube elements having a leg portion extending from one side of the hot gas conduit to the other, a leg portion extending from the other side back to the first side, and being interconnected so as to define a serpentine flow path for a cooling medium.

3. A cooling device according to claim 2 including inlet and outlet headers connected to respective opposite ends of said tubes for the inflow of a cooling medium and the outf low of a cooling medium.

4. A cooling device according to claim 1 wherein said registers each include combined inlet and outlet header, a mounting plate closing one side of said hot gas conduit, each of said head is being mounted in spaced relationship on said mounting plate, said tube comprising a passage defining back and forth flow through said hot gas conduit being connected at respective ends to said inlet and outlet headers.

5. A cooling device according to claim 4 wherein said hot gas conduit includes an end being located adjacentthe hot gas supply and a plurality of damper control elements connected to said end for adjusting said end relative to the gas supply so asto 3 GB 2 027 535 A 3 provide an air gas at the end thereof for the airflow of air thereto.

6. A cooling device according to anyone of claims 1 to 5, wherein each of said registers includes a common water inlet tank and a common water outlet tank connected to respective ends of said tubes.

7. A cooling device according to claim 1, wherein each of said registers include a serpentine tube forming a flow space extending backwardly and forwardly through said conduit, the longitudinally spaced ones of said registers having serpentine tubes which are offsetwith respeetto each other.

8. A cooling device according to claim 1 includ- ing a common baseplate mounting all of said registers on saidhot gas conduit.

9. A cooling device as herein before described with reference to and as illustrated in the accompanying drawings.

Printed for Her Majesty's Stationery Office by Croydon Printing Company Limited, Croydon Surrey, 1980. Published by the Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.